"The study does suggest that for some people, they may be of benefit, particularly in terms of pain relief and muscle stiffness," says Alan Thompson, at the National Hospital for Neurology and Neurosurgery in London, UK, and co-leader of the research. Thompson and his colleagues divided their 630 patients into three groups. The first received 9-tetrahydrocannabinol (THC), the main active ingredient of cannabis. The second group received a cannabis plant extract, and the third a placebo.

Muscular Stiffness
The investigators particularly wanted to find out whether the drugs could ease symptoms of spasticity, the muscular stiffness and jerky movements that afflict patients with MS.

Standard objective tests to measure the severity of spasticity suggested the drugs were no more
effective than the placebo. But 60 per cent of treated patients reported a reduction in spasticity, compared with 46 per cent who received the placebo.

Furthermore, 54% of the treated patients reported pain relief compared with 37% receiving the placebo. "This suggests cannabinoids may benefit some patients," says Thompson. However, the researchers note some of the patient's receiving cannabis became "light-headed", meaning they realised they were receiving the drug rather than the placebo - which might affect the subjective ratings.

But the UK Multiple Sclerosis Society says the results reinforce the need for researchers to focus as much on how patients say they feel as on what the tests measure. The society is calling for cannabis-based drugs of proven benefit to be made available through the UK's National Health Service.

Evidence Base
In a commentary on team's paper in The Lancet, Luanne Metz and Stacey Page, at the University of Calgary, Canada, note: "We now have as much evidence to support the use of these oral cannabinoids - as we do for many standard therapies for spasticity." The UK's National Institute for Clinical Excellence is evaluating the potential for cannabis-based medicines, but its advice is not expected next June.

Britain's drug approval authorities are also midway through evaluating an application to sell a  cannabinoid-based painkiller. If it is approved, the government has promised to amend the law classifying cannabis as an illegal drug to allow the medicine based on it to be given legally.

In the meantime, the researchers have warned patients against smoking marijuana to relieve symptoms. "The major problem with smoking is making sure you know how much active component is in the blood, and the second problem is the cancer risk," says Thompson.

Journal reference: The Lancet (vol 362, 1517)    http://www.newscientist.com/article.ns?id=dn4356